If Housing New Zealand continues to spend at the same rate, it'll end up costing the taxpayer around $10 million for the year.

Just last month in Christchurch, a quarter of the 19 units in a Housing New Zealand block were found to be contaminated. Yet the number of Kiwis using P has hardly changed in the past three years. It remains at just under 1 percent.

The reason is more people are having their properties tested, and not only Housing New Zealand tenants.

There is another aspect to the P problem and that's needy families missing out on houses, while around 400 state houses can't be filled because they're contaminated.

A Christchurch couple is urging others to learn from their misfortune after tenants ruined their property with methamphetamine. The bill has run into hundreds of thousands of dollars and took them to breaking point.

Mark Hutchinson-Lowden and LeeAnn Harlen had intended to make their small Christchurch house their retirement investment.

"She pulled the cupboard out and found the two P pipes in there. And that's when all hell broke loose," says Mr Hutchinson-Lowden.

They'd spent $180,000 renovating the house before tenants moved in last year.

Less than three months later, they'd evicted the tenants and it was discovered someone had been cooking meth in the house.

It's been a stressful and expensive journey since.

"Every time I come to this house it brings back bad memories, and there are four people in my life who helped me get through this. And if it wasn't for them, I probably wouldn't be here," says Mr Hutchinson-Lowden.

He says the total bill of decontaminating the house and rebuilding much of it from scratch has cost more than $120,000. He's managed to have that covered by insurance, after putting up a fight.

Ms Harlen says landlords should be routinely checking for P between tenants.

"I think landlords have got to be very aware of doing the right thing. You can't ignore it, really."

She warns those who don't could be liable if a house is found to be contaminated.

But it's not something the couple will ever have to do again for either of their rental properties; they're selling both.

"We have to walk away and just take what money we've got left in these places and have a simple life," says Mr Harlen.